Observation balloons were raised with an observer in a basket, equipped with binoculars, a radio, and sometimes a parachute. They were usually raised behind enemy lines but quickly became easy prey for a fighter plane. They were filled with highly-flammable hydrogen and could be ignited with a few well-placed incendiary rounds. Here we see 1) French soldiers inflating a balloon using cylinders of hydrogen mounted on trucks. 2) German troops watching on as a balloon begins its ascent on the Western Front. 3) A British balloon hovering above Ypres, and 4) A remarkable photo showing two German balloons being shot down near Boyelles, France. #danielsaeroplanes#aviation#aviationhistory#aircraft#flying#flight#pilotlife#pilots#adventure#fighter#fighterpilot#WWI#planeporn